Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.89	3.740%	$139.9349	$139.93	$139.95	$139.90
Purchase #2	$117.76	8.523%	$127.7967	$127.80	$127.80	$127.80
Purchase #3	$99.70	3.563%	$103.2523	$103.25	$103.25	$103.30
Purchase #4	$243.87	5.177%	$256.4951	$256.50	$256.50	$256.50
Purchase #5	$103.26	13.623%	$117.3271	$117.33	$117.35	$117.30
Purchase #6	$147.84	3.210%	$152.5857	$152.59	$152.60	$152.60
Purchase #7	$208.34	12.447%	$234.2721	$234.27	$234.25	$234.30
7 purchase totals =	$1,055.66		$1,131.6639	$1,131.67	$1,131.70	$1,131.70